As the number of Seattle bike officers grew, so did the national trend. In 2003, the most recent year with specific statistics, 45 percent of U.S. police departments and 16 percent of sheriff's offices were using bicycles, Becker said.

Former Seattle officers Paul Grady and Mike Miller were the first to start on mountain bikes in July 1987.

Within a half-hour of starting, the pair busted a group of cocaine users near Post Alley. In August of that year, three bike patrol officers made 507 arrests. By the summer of 1991, the department had a dozen bike officers.

"Literally every day we told ourselves 'You know, these are going to be the best years of our career,' " said Lt. Eric Barden, who was one of those first 12 officers. "We had a blast."

New Seattle bike officers go through a 40-hour training that includes handling skills and obstacle avoidance. They typically stay with the squad three to five years.

The West Precinct has four bike squads, and the only time their spokes aren't rolling is when it snows or is below freezing, said Sgt. Brian Kraus, who oversees the five-person night squad.

The bike squads are known for regulating tailgaters after Seahawks games, and they use crowd-control techniques developed during the 1999 WTO protests.

Though Seattle police do not keep track of arrests specifically by bike officers, Kraus said narcotics arrests, including organized busts in city parks, account for most of them.

"We would typically beat the patrol cars on hot calls in progress because of the traffic situation," Barden said.

That is why police say they've become an essential element in regulating crowds around rowdy downtown nightclubs.

About 10:30 p.m. on Fridays and Saturdays, Kraus rolls his patrol car through Belltown and Pioneer Square, checking parking lots and scanning the number of people on the streets.

Kraus then has officers roll to the hot spots.

"When people see a fight, they'll look for us to come and get the bad guy," Cierley said on a recent Saturday, patrolling First Avenue and Bell Street. "When we come in, it's like parting the Red Sea."

On Nov. 10, he and Vaca were in Belltown. They heard a gunshot near Western Avenue and Bell Street. They biked up the block.

Within minutes they found witnesses who told them about a Lexus crashing into a condominium, men fighting near the car and the gunshot that followed, police said.

After jotting down the Lexus' license plate from witnesses, officers got Renton police to check an address. The suspect was arrested later that night.